--- a/python/events.py	Tue Feb 11 02:55:02 2014 -0500
+++ b/python/events.py	Thu Feb 13 01:24:27 2014 -0500
@@ -67,6 +67,7 @@
         self.roadUser2 = roadUser2
         self.categoryNum = categoryNum
         self.indicators = {}
+        self.interactionInterval = None
 
     def getRoadUserNumbers(self):
         return self.roadUserNumbers
@@ -141,8 +142,20 @@
         self.videoFilename= videoFilename	
 
     def addInteractionType(self,interactionType):
-	''' interaction types: conflict or collision if they are known'''
-        self.interactionType= interactionType			
+	    ''' interaction types: conflict or collision if they are known'''
+        self.interactionType= interactionType
+
+    def computeInteractionInterval(self):
+        ''' Computes the times during which the road users are getting closer,
+        ie the collision course angle is positive
+        (Other thresholds/indicators could be tried)'''
+        collisionCourseDotProducts = self.getIndicator(Interaction.indicatorNames[0])
+        inter = collisionCourseDotProducts.getTimeInterval()
+        interactionInstants = [t for t in inter if collisionCourseDotProducts[t] >= 0]
+        if len(interactionInstants) >= 2:
+            self.interactionInterval = moving.TimeInterval(interactionInstants[0], interactionInstants[-1])
+        else:
+            self.interactionInterval = moving.TimeInterval()
 
 def createInteractions(objects):
     '''Create all interactions of two co-existing road users